open a program like Notepad... and let it sit. See if characters are depressed. Such as 5,1, ect. id say theres a short, faulty switch, or ipac trouble.
try replacing the micros with new ones. maybe they are the blame.
ive seen a ghost only once in 32 years of life, and it was a very rare event. even rare-er is a ghost that can actually interact with the physical world (poltergeist). And if it was one of them, youd see the buttons actually depress.